Fix packaging outputs commands

There were a few issues with the output packaging process that were
found during testing of the general-tests optimization.

First and foremost is that the packaging commands were trying to be
created before the build ran, when the outputs don't exist. I've changed
the logic to just collect the methods themselves which will then be run
during build plan execution after the build has completed.

A few other smaller issues include fixing the path to the soong_zip
binary, incorrect execution of the soong dumpvars command, and not
building the shared libs zip.

Test: atest build_test_suites_test; atest optimized_targets_test
Bug: 358215235
Change-Id: I8a3f54738f8bb5d871aadf7423844076c38b54a6